1. Field of the Invention
The present invention relates generally to emergency signaling devices, and more particularly to a safety whistle which can be blown to help locate a person in distress.
2. Background Art
Mouth blown whistles are an effective tool for helping to locate a person in an emergency. For example, sportsmen are well advised to carry a whistle in order to aid searchers in the event they become lost in a wilderness or on a body of water.
Traditional whistles have proven reasonably effective for this purpose. For example, the traditional "Thunderer" style whistle, which holds a cork pea in a chamber at the end of an air passage, produces a strong, clear note with a "warbling" effect which helps draw attention. Nevertheless, these traditional devices are not without their deficiencies.
Firstly, traditional whistles emit only a single tone, which is not ideal in many emergency scenarios. For example, it is well known that high-pitched tones are generally easier for people to localize, but they do not carry well over long distances. Lower-pitched tones by contrast, are generally perceptible at longer distances, but it is difficult for the human ear to determine the actual location of their source. This deficiency can be critical in real world situations: for example, a person lost in the woods or on a body of water may initially be a significant distance from rescuers, so that a high-pitched tone would not reach them; however, when the searchers are closer, higher tones are needed to help them localize the source quickly.
In addition, traditional whistles are not well adapted in terms of structure for use in the hostile and often severe environments in which emergencies frequently occur. For example, traditional whistles are typically meant to be held to the mouth by a hand, but a person who is using their arms to stay afloat will be unable to do this. Even if the person has their hands free, wet or extreme cold may severely impair their ability to grip the device; for example, in severe cold the person will either be wearing heavy gloves, which will impair achieving any sort of grip, or else their hands will tend to become so numb and stiff as to be virtually useless.
Moreover, hostile environmental conditions may also make it difficult to effectively blow air through a whistle. In particular, severe cold and/or fatigue can make it very difficult for a person to seal their lips around a mouthpiece, with the result that much of the air escapes uselessly. Similarly, a person who has been gasping for air, as when trying to stay afloat, will find it difficult to hold the device in their mouth, and to form an effective seal between breaths. The severity of this problem is aggravated by the fact that it is often essential for the person to blow the whistle continuously and without interruption if there is to be any hope of rescue, as, for example, when a person is lost overboard at night or in a fog and therefore cannot know whether rescue boats are near.
Accordingly, there exists a need for a whistle which can emit tones at both high and low pitches, so as to facilitate the detection of persons in distress from relatively long distances, and the localization of such persons by searchers closer to the scene. Moreover, there is a need for such a whistle which is easy to grip with impaired hands, and which may in fact be held in the mouth without the aid of one's hands. Still further, there exists a need for such a whistle which a a person can correctly position in his mouth and form an effective lip seal therewith, even under conditions of severe cold, wet, and fatigue.